build(deps): bump thor in /appengine/rails-cloudsql-mysql (#1579)

Bumps [thor](https://github.com/rails/thor) from 1.2.2 to 1.4.0.
- [Release notes](https://github.com/rails/thor/releases)
- [Commits](rails/thor@v1.2.2...v1.4.0)

---
updated-dependencies:
- dependency-name: thor
  dependency-version: 1.4.0
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

appengine/rails-cloudsql-mysql/Gemfile.lock

@@ -329,7 +329,7 @@ GEM
     stackdriver-core (1.5.0)
       google-cloud-core (~> 1.2)
     stringio (3.1.0)
-    thor (1.2.2)
+    thor (1.4.0)
     tilt (2.3.0)
     timeout (0.4.3)
     tzinfo (2.0.6)